Color-Kinematics Duality in the Cosmological Grassmannian

Abstract: In this paper, we show that the cosmological Grassmannian provides a unified framework for studying several structures familiar from flat-space amplitudes, including Jacobi identities for Yang--Mills kinematic numerators, color--kinematics duality, double- and $s$-copy relations, and differential BCJ relations. For example, we show that the four-point gluon correlator gives exact kinematical Jacobi identity $n_s+n_t+n_u=0,$ and the graviton correlator obtained from the color-kinematics double copy agrees with the corresponding BCFW result upto terms regular in all the exchange channels.